get longest palindrome

DIRECTORY.md

@@ -79,6 +79,7 @@
     * [Egg Dropping](https://github.com/TheAlgorithms/Rust/blob/master/src/dynamic_programming/egg_dropping.rs)
     * [Fibonacci](https://github.com/TheAlgorithms/Rust/blob/master/src/dynamic_programming/fibonacci.rs)
     * [Fractional Knapsack](https://github.com/TheAlgorithms/Rust/blob/master/src/dynamic_programming/fractional_knapsack.rs)
+    * [Get Length Of The Palindrome With Max Length](https://github.com/TheAlgorithms/Rust/blob/master/src/dynamic_programming/get_length_of_the_palindrome_with_max_length.rs)
     * [Is Subsequence](https://github.com/TheAlgorithms/Rust/blob/master/src/dynamic_programming/is_subsequence.rs)
     * [Knapsack](https://github.com/TheAlgorithms/Rust/blob/master/src/dynamic_programming/knapsack.rs)
     * [Longest Common Subsequence](https://github.com/TheAlgorithms/Rust/blob/master/src/dynamic_programming/longest_common_subsequence.rs)

src/dynamic_programming/get_length_of_the_palindrome_with_max_length.rs

@@ -0,0 +1,66 @@
+/*
+Find the longest palindrome substring in the string（non-unique solution）
+Source：https://leetcode.cn/problems/longest-palindromic-substring/description/
+Example:
+
+Input: s = "abdbc"
+Output: "bdb"
+*/
+
+pub fn get_length_of_the_palindrome_with_max_length(s: &str) -> String {
+    if s.is_empty() {
+        return "".to_string();
+    }
+    let s: Vec<char> = s.chars().collect();
+    let n = s.len();
+    let mut dp = vec![vec![true; n]; n];
+    // res is the index of the longest palindrome
+    let mut res = (0, 0);
+
+    // form filling strategy: fill in the form by
+    // use k instead of palindrome length
+    for k in 1..n {
+        for i in 0..(n - k) {
+            if k == 1 {
+                // strings of 2 equal characters are palindromes
+                dp[i][i + k] = s[i] == s[i + 1];
+            } else {
+                // a string that is equal on both sides and has a palindrome in the middle is also a palindrome
+                dp[i][i + k] = (s[i] == s[i + k]) && dp[i + 1][i + k - 1];
+            }
+
+            if dp[i][i + k] {
+                res = (i, i + k);
+            }
+        }
+    }
+    s[res.0..=res.1].iter().collect::<String>()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::get_length_of_the_palindrome_with_max_length;
+    macro_rules! test_get_length_of_the_palindrome_with_max_length {
+        ($($name:ident: $inputs:expr,)*) => {
+            $(
+                #[test]
+                fn $name() {
+                    use crate::string::is_palindrome;
+                    let (s, expected) = $inputs;
+                    assert!(is_palindrome(expected));
+                    assert_eq!(get_length_of_the_palindrome_with_max_length(s), expected);
+                    assert_eq!(get_length_of_the_palindrome_with_max_length(expected), expected);
+                }
+            )*
+        }
+    }
+    test_get_length_of_the_palindrome_with_max_length! {
+        empty_input: ("", ""),
+        basic_1: ("abdbc", "bdb"),
+        basic_2: ("abyxycbabcyxy", "yxycbabcyxy"),
+        // Theoretically it is possible to return either aa or bb,
+        // there are multiple palindromes of the same length, here only the rightmost one is returned
+        basic_3: ("aabb", "bb"),
+        unicode_1: ("常威天天打来福", "天天"),
+    }
+}

src/dynamic_programming/mod.rs

@@ -2,6 +2,7 @@ mod coin_change;
 mod egg_dropping;
 mod fibonacci;
 mod fractional_knapsack;
+mod get_length_of_the_palindrome_with_max_length;
 mod is_subsequence;
 mod knapsack;
 mod longest_common_subsequence;
@@ -28,6 +29,7 @@ pub use self::fibonacci::memoized_fibonacci;
 pub use self::fibonacci::nth_fibonacci_number_modulo_m;
 pub use self::fibonacci::recursive_fibonacci;
 pub use self::fractional_knapsack::fractional_knapsack;
+pub use self::get_length_of_the_palindrome_with_max_length::get_length_of_the_palindrome_with_max_length;
 pub use self::is_subsequence::is_subsequence;
 pub use self::knapsack::knapsack;
 pub use self::longest_common_subsequence::longest_common_subsequence;